1. Field of the Invention
The present invention relates to a device and method for producing gas solution, such as hydrogen solution, ozone solution, or the like, for preferable use in cleaning of substrates or the like used in production of electronic components and other such devices, and also to a cleaning device employing the gas solution producing device.
2. Description of the Related Art
In the field of electronic devices (semiconductor devices, LCD panels, and so on), a step of cleaning substrates (semiconductor or glass substrates, and so on) is included in all production process. During cleaning, foreign objects, including organic material (e.g., particles, photoresists, and so on) in the atmosphere in a clean room, which have become attached to the substrates must be removed. There is therefore great interest in cleaning solutions superior in cleaning performance and preferable for use in such cleaning. Some candidates of such solution are ozone solution and hydrogen solution, and so on, which can be obtained by dissolving gas (ozone, hydrogen, and so on) in deionized water. As a method for dissolving these gases into deionized water, a method for bringing gas into contact with deionized water via hollow fiber membrane is well known conventionally.
FIG. 13 is a diagram showing a conventional ozone solution producing device 90. The ozone solution producing device 90 mainly comprises an ozone producing device 91 and a gas dissolving module 92. The gas dissolving module 92 is, for example, a cylinder vessel accommodating a number of hollow fiber membranes, and supplied with ozone gas produced in the ozone producing device 91, as well as deionized water. When ozone gas and deionized water are introduced into the gas dissolving module 92, the ozone gas flows into each hollow fiber membrane, while the deionized water fills interior space of the vessel. Then, when the ozone gas and deionized water come into contact with each other via the hollow fiber membranes, the ozone gas is dissolved into the deionized water and an ozone solution consisting of ozone dissolved in deionized water is produced. The resultant ozone solution is supplied to, for example, a nozzle 93 of a cleaning device, for use in cleaning.
The above-mentioned conventional ozone solution producing device, however, has the following shortcomings. The conventional electrolytic ozone producing device for general use is constructed, for protection of the electrodes, such that ozone production cannot be suspended. Moreover, as the starting up of a gas dissolving module requires a relatively longer period of time, ozone production must be continued to ensure stable ozone concentration. Thus, there is no choice but to discard unused ozone solution. In addition, as the ozone producing device and the gas dissolving module are directly connected to each other via a pipe, ozone gas is always supplied to the gas dissolving module whether or not ozone solution is used. In other words, while ozone solution is not used, ozone gas is wastefully thrown away. This results in a very inefficient device.
In order to improve the efficiency of such equipment, there has been proposed a structure in which a valve is provided in a pipe connecting the ozone producing device and the gas dissolving module. With this structure, the valve is closed while ozone solution is not used, to thereby stop supply of ozone gas. As a result, waste of ozone gas can be prevented. However, generally, as the total capacity of the hollow fiber membranes in an ozone solution producing equipment is relatively large compared to the amount of ozone gas produced, a relatively long time is required before the ozone gas concentration in the hollow fiber membranes becomes stabilized in a normal condition after supply of ozone gas is resumed. This results in a long time before ozone concentration of the ozone solution reaches a predetermined value, or a long start-up time, and thus an equipment of a reduced operation rate.
On the other hand, where ozone solution may be needed quickly for cleaning, a constant supply of ozone gas to the gas dissolving module must be maintained. Not only may this result in a waste of ozone gas, provision of the valve becomes meaningless.
In addition, components of the above-mentioned equipment, including pipes, must be highly pressure resistive as pressure increases on the ozone producing device side when the valve is closed, particularly, for a long time.